Advantage distillation is a well-known approach to a cryptographic key agreement protocol. An example of a system that exploits advantage distillation is a quantum cryptographic system, although other exemplary systems, such as those based on receiving random or pseudo-random sequences of 0s and 1s from satellite or terrestrial transmissions, including radio frequency (RF) transmissions, have also been proposed.
A system that exploits advantage distillation may include a source of bits (S) and two legitimate receivers (A, B). If an eavesdropper (E) does not have perfect reception of the random bits (S), then A and B can agree on random numbers derived from the S bits in such a way that E essentially has no knowledge of the random numbers, even if E has a much better receiver than A or B.
In order to perform advantage distillation, A and B communicate via a public communications channel regarding the bits they received well. The well-received bits are used to create a shorter random number. The greater the ratio of the original length of the random sequence to this shorter random number, the greater the assurance that E will have little or no knowledge of the shorter random number.
Such a system may use a flow of secret bits that may be used as cryptographic key material to which the system adds and consumes over time. Such systems provide the key material on a first-come, first-served basis. It would be advantageous for a process that requires a flow of secret bits to be able to reserve a particular rate of secret bits in order to guarantee the availability of the secret bits to the process when needed. Current systems that exploit advantage distillation do not provide such a feature.